So if I am hearing this correctly I have four options.
1) My original idea, but if I use two 50 watt heads I might as well hook one 100 watt (YBA-1a) head to my cab, so that's out. I could buy two 100 watt heads but I can't afford that. Then there is the possibility of phase issues.
Not worth the hassle. Traynors are nice but that 50 watts runs out in a hurry unless you have a loud cab. You'd be better off just getting a bigger cab than trying this.
2) Use a "dummy load" with the Traynor and run it into a solid-state power amp - I'm sure my Eden WT-600 would work for that. But then, I lose the tube output stage.
Yep, you'll lose the tube output feel and probably kill your output tubes in short order. Devices like the THD Hotplate are great ways to kill power tubes.
3) Buy a YBA-200, which is the easiest and possibly cheapest thing to do, so I really hope I find a similar tone in them when I go to the city to test drive one.
From what I hear, it's brighter and "gainier" than old Traynors, so you'd have to do a fair amount of tube swapping to make it sound close to your old one.
4) Find a YBA-3 or YBA-3a (Custom Special or Super Custom Special, respectively). That would be a gamble since I do not know if they sound anything at all like the YBA-1. They are definitely loud enough. But alas they are hard to find anyway.
I've played a Super Custom Special. It's voiced darker, like an Ampeg, but still has that Traynor cut.